Barcode reader having multiple illumination systems and multiple sets of imaging optics

ABSTRACT

According to one aspect of the invention, there is provided a barcode reader, comprising a first illumination system that emits first illumination with a first illumination spectrum, and a second illumination system that emits second illumination with a second illumination spectrum. The second illumination spectrum is broader than the first illumination spectrum. The barcode reader also comprises a first lens assembly with a first optical path through the first lens assembly to a first image sensor section. The first optical path includes a first filter configured to pass an acceptance spectrum of electromagnetic radiation and attenuate an attenuated spectrum of electromagnetic radiation. The first illumination spectrum is primarily composed of the acceptance spectrum. The barcode reader also comprises a second lens assembly with second optical path through the second lens assembly to a second image sensor section.

CLAIM OF PRIORITY

This application is a continuation-in-part of U.S. patent applicationSer. No. 13/946,862, titled “Selecting Illumination Characteristics ThatWill Be Most Suitable For Reading A Barcode,” filed Jul. 19, 2013, withinventors Ming Lei and Ryan Hoobler.

This application is also a continuation-in-part of U.S. patentapplication Ser. No. 14/062,743, titled “Diffuse Bright FieldIllumination System For A Barcode Reader,” filed Oct. 24, 2013, withinventors Ming Lei and George Powell.

TECHNICAL FIELD

The present disclosure relates generally to barcode readers. Morespecifically, the present disclosure relates to a barcode reader thatincludes multiple illumination systems and multiple sets of imagingoptics.

BACKGROUND

A barcode is an optical machine-readable representation of information.Devices for identifying or extracting information from barcodes aregenerally referred to as barcode readers (or barcode scanners). Animage-based barcode reader includes a camera for capturing an image of abarcode to be read. The camera includes a focusing lens that focuseslight reflected from a target area onto a photo sensor array. Once animage of a barcode has been captured by the camera, a decoder processesthe image and extracts the information contained in the barcode.

SUMMARY

According to one aspect of the invention, there is provided a barcodereader, comprising a first illumination system that emits firstillumination with a first illumination spectrum, and a secondillumination system that emits second illumination with a secondillumination spectrum. The second illumination spectrum is broader thanthe first illumination spectrum. The barcode reader also comprises afirst lens assembly with a first optical path through the first lensassembly to a first image sensor section. The first optical pathincludes a first filter configured to pass an acceptance spectrum ofelectromagnetic radiation and attenuate an attenuated spectrum ofelectromagnetic radiation. The first illumination spectrum is primarilycomposed of the acceptance spectrum. The barcode reader also comprises asecond lens assembly with second optical path through the second lensassembly to a second image sensor section.

Alternatively or additionally, the attenuated spectrum includesfrequencies of visible light not included in the first illuminationspectrum.

Alternatively or additionally, the first illumination spectrum includeselectromagnetic radiation primarily from 650 nm to 700 nm.

Alternatively or additionally, the second illumination spectrum includeselectromagnetic radiation primarily from 400 nm to 700 nm.

Alternatively or additionally, the first illumination system is a darkfield illumination system. The dark field illumination system emits thefirst illumination towards the first optical path at an emission anglethat is less than 45 degrees from a plane that is perpendicular to thefirst optical path.

Alternatively or additionally, the dark field illumination systemcomprises a first set of illumination sources positioned to a right sideof the first and second lens assemblies and a second set of illuminationsources positioned to a left side of the first and second lensassemblies.

Alternatively or additionally, the barcode reader further comprisescontrol circuitry that independently controls intensity of the first setof illumination sources and the second set of illumination sources.

Alternatively or additionally, the dark field illumination systemcomprises a back lit illumination diffusor emitting the firstillumination towards the first optical path at the emission angle.

Alternatively or additionally, the dark field illumination systemcomprises a refracting diffusor through which the first illumination isemitted towards the first optical path at the emission angle, andillumination enters the refracting diffusor at an entry angle that isdifferent than the emission angle.

Alternatively or additionally, the entry angle is substantially parallelto the first optical path.

Alternatively or additionally, the entry angle is substantiallyperpendicular to the emission angle.

Alternatively or additionally, the second illumination system is adiffuse bright field illumination system. The diffuse bright fieldillumination system comprises an optical substrate with a front majorsurface and a back major surface, each of which is substantiallyperpendicular to an optical path of the barcode reader. The front majorsurface faces a field of view of the first and second lens assemblies.The diffuse bright field illumination system further comprises at leastone illumination source propagating illumination between the front majorsurface and the back major surface. The diffuse bright fieldillumination system further comprises extraction features causing thesecond illumination to exit the front major surface into the field ofview of the first and second lens assemblies.

According to another aspect of the invention, there is provided abarcode reader comprising an image sensor configured to capture an imageof a barcode within a field of view of the image sensor. The barcodereader further comprises a first set of imaging optics and a second setof imaging optics, each for providing a corresponding image of thebarcode on the image sensor. The barcode reader further comprises afirst illumination system and a second illumination system, each forilluminating at least a part of the field of view with a respectivefirst illumination spectrum and a second illumination spectrum differentfrom the first illumination spectrum. The first set of imaging opticsand the second set of imaging optics respond differently to thedifferent illumination spectrums.

Alternatively or additionally, the barcode reader further comprises ahousing. The first set of imaging optics and the second set of imagingoptics are positioned within the housing such that there is a firstoptical path through the first set of imaging optics to a first portionof the image sensor and a second optical path through the second set ofimaging optics to a second portion of the image sensor.

Alternatively or additionally, the first optical path is different fromthe second optical path.

Alternatively or additionally, the first portion of the image sensorcorresponds to approximately a first half of the image sensor and thesecond portion of the image sensor corresponds to approximately a secondhalf of the image sensor.

Alternatively or additionally, the image sensor comprises a first imagesensor and a second image sensor. The first image sensor includes thefirst portion of the image sensor and the second image sensor includesthe second portion of the image sensor.

Alternatively or additionally, the first set of imaging optics includesa filter configured to pass an acceptance spectrum of electromagneticradiation and attenuate an attenuated spectrum of electromagneticradiation.

Alternatively or additionally, the first illumination spectrum includesthe acceptance spectrum.

Alternatively or additionally, the first illumination spectrum isprimarily composed of the acceptance spectrum.

Alternatively or additionally, the attenuated spectrum includesfrequencies of visible light not included in the first illuminationspectrum.

Alternatively or additionally, the first illumination spectrum includeselectromagnetic radiation primarily from 650 nm to 700 nm.

Alternatively or additionally, the second illumination spectrum includeselectromagnetic radiation primarily from 400 nm to 700 nm.

Alternatively or additionally, the first illumination system includes abright field illumination system that directs bright field illuminationhaving the first illumination spectrum into the field of view of theimage sensor. The first illumination system also includes a dark fieldillumination system that directs dark field illumination into the fieldof view of the image sensor. The second illumination system includes adiffuse bright field illumination system that directs diffuse brightfield illumination having the second illumination spectrum into thefield of view of the image sensor.

Alternatively or additionally, the bright field illumination system andthe diffuse bright field illumination system direct illumination intothe field of view of the image sensor substantially parallel to anoptical path that runs through a set of imaging optics to a portion ofthe image sensor.

According to another aspect of the invention, there is provided abarcode reader comprising a first illumination system that emitsillumination with a first illumination spectrum, a second illuminationsystem that emits illumination with a second illumination spectrum, andan image sensor configured to capture an image of a barcode within afield of view of the image sensor. The barcode reader further comprisesa first set of imaging optics and a second set of imaging optics, eachproviding a corresponding image of the barcode on the image sensor. Thefirst set of imaging optics is configured to focus an image of thebarcode, when illuminated by the first illumination system, with asuperior contrast profile than when illuminated by the secondillumination system. The second set of imaging optics is configured tofocus an image of the barcode, when illuminated by the secondillumination system, with a superior contrast profile than whenilluminated by the first illumination system.

Alternatively or additionally, the first illumination system is a darkfield illumination system. The dark field illumination system emits theillumination of the first illumination spectrum into the field of viewof the image sensor at an angle that is less than 45 degrees from aplane that is perpendicular to an optical path from the image sensorthrough the first set of imaging optics into a center of a field of viewof the first set of imaging optics.

Alternatively or additionally, the dark field illumination systemcomprises a first set of illumination sources positioned to a right sideof the first and second sets of imaging optics and a second set ofillumination sources positioned to a left side of the first and secondsets of imaging optics.

Alternatively or additionally, the barcode reader comprises controlcircuitry that independently controls intensity of the first set ofillumination sources and the second set of illumination sources.

Alternatively or additionally, the dark field illumination systemcomprises a back lit illumination diffusor emitting the firstillumination towards the first optical path at the emission angle.

Alternatively or additionally, the dark field illumination systemcomprises a refracting diffusor through which the first illumination isemitted towards the first optical path at the emission angle.Illumination enters the refracting diffusor at an entry angle that isdifferent than the emission angle.

Alternatively or additionally, the entry angle is substantially parallelto the first optical path.

Alternatively or additionally, the entry angle is substantiallyperpendicular to the emission angle.

Alternatively or additionally, the second illumination system is adiffuse bright field illumination system comprising an optical substratewith a front major surface and a back major surface, each of which issubstantially perpendicular to an optical path of the barcode reader.The front major surface faces a field of view of the first and secondlens assemblies. At least one illumination source propagatesillumination between the front major surface and the back major surface.The diffuse bright field illumination system further comprisesextraction features causing the second illumination to exit the frontmajor surface into the field of view of the first and second lensassemblies.

A number of features are described herein with respect to embodiments ofthe invention; it will be appreciated that features described withrespect to a given embodiment also may be employed in connection withother embodiments.

The invention includes the features described herein, including thedescription, the annexed drawings, and, if appended, the claims, whichset forth in detail certain illustrative embodiments. These embodimentsare indicative, however, of but a few of the various ways in which theprinciples of the invention may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top-down view of a barcode reader in accordance with thepresent disclosure.

FIGS. 2A-2E are front views of different embodiments of an opticalsubstrate within the barcode reader shown in FIG. 1.

FIGS. 3A-3F illustrates cross-sectional views of different embodimentsof the optic, taken along line A-A in FIGS. 2A-2C.

FIGS. 4A-4C are cross-sectional views of alternative embodiments of theoptical substrate.

FIG. 5 is a top-down view of another embodiment of a barcode reader inaccordance with the present disclosure.

FIG. 6 is a top-down view of another embodiment of a barcode reader inaccordance with the present disclosure.

FIG. 7 is a top-down view of an additional embodiment of a barcodereader in accordance with the present disclosure.

FIGS. 8A-8B are cross-sectional views of tertiary light sourcesilluminating the optical substrate in two embodiments of the barcodereader.

FIG. 9 illustrates one configuration of a barcode reader in accordancewith the present disclosure.

FIG. 10 illustrates an example of a method that may be performed by theillumination selection circuitry of the barcode reader in accordancewith the present disclosure.

FIG. 10A illustrates an example showing the relative size of a testimage compared with a subsequent image.

FIG. 11 illustrates another example of a method that may be performed bythe illumination selection circuitry in accordance with the presentdisclosure.

FIG. 12 illustrates one example of a single test image comprising aplurality of window images.

FIG. 12A illustrates another example of a single test image comprising aplurality of window images.

FIG. 13 illustrates another example of a method that may be performed bythe illumination selection circuitry in accordance with the presentdisclosure.

FIGS. 14A and 14B illustrate a plurality of test images comprising aplurality of window images.

FIG. 15 illustrates another example of a method that may be performed bythe illumination selection circuitry in accordance with the presentdisclosure.

FIG. 16 illustrates another example of a method that may be performed bythe illumination selection circuitry in accordance with the presentdisclosure.

FIG. 17 illustrates another example of a method that may be performed bythe illumination selection circuitry in accordance with the presentdisclosure.

FIG. 18 illustrates various components that may be utilized in a barcodereader.

FIG. 19 illustrates a front view of a barcode reader in accordance withthe present disclosure.

FIG. 20 illustrates a side view of the barcode reader shown in FIG. 19.

FIG. 21 illustrates a side view of an alternative embodiment of thebarcode reader shown in FIG. 19.

DETAILED DESCRIPTION

The present invention provides a barcode reader for imaging a barcodeusing diffuse light. The barcode reader illuminates a barcode using anillumination system including an optical substrate. Light introducedinto the optical substrate by at least one light source propagatesbetween a front major surface and a back major surface in a directiontransverse to an optical axis of a camera. Light is mixed by totalinternal reflection as its travels within the optical substrate and oneor more extraction features included in the optical substrate allowlight to be removed from the optical substrate in a directed intensitypattern. By allowing the light to mix as it propagates within theoptical substrates, the propagating light loses any structure impartedonto it by the one or more light sources. By illuminating the barcodewith unstructured light, it is possible to more accurately and quicklyread the information contained in the imaged barcode.

FIG. 1 is a top-down view of a barcode reader 100 in accordance with thepresent disclosure. The barcode reader 100 includes a housing 101, acamera 103, and an illumination system 105. The barcode reader 100illuminates a barcode with the illumination system 105 and captures animage of the barcode using the camera 103.

The camera 103 is located within the housing 101 and is configured tocapture an image of a barcode within a field of view 106 of the camera103. The field of view 106 of the camera 103 is directed along anoptical axis 114 of the camera 103. The camera may include a photosensor array 102 and a lens 104 that focuses illumination reflected fromobjects (e.g., a barcode) within the field of view 106 onto the photosensor array 102. The optical axis of the camera 103 may be the opticalaxis of the lens 104. The camera 103 may be located near a center of theoptical substrate 122 in one or more of the vertical dimension and thehorizontal dimension.

As will be understood by one of ordinary skill in the art, the camera103 may comprise any device capable of capturing an image of a field ofview. For example, the photo sensor array 102 may comprise any detectorcapable of measuring or quantifying light incident on the pixel array ofthe detector. The detector may comprise, for example, an image sensor,CCD sensor, CMOS sensor, or any device capable of measuring orquantifying light incident on the pixel array of the detector.Similarly, the lens may comprise a single lens or series of lensescapable of focusing light onto the photo sensor array 102. Furtherdetails regarding specific embodiments of the camera 103 are discussedbelow.

The illumination system 105 is configured to illuminate the barcodewhile the camera 103 captures an image of the barcode. The illuminationsystem 105 includes at least one light source 120 and an opticalsubstrate 122 including one or more extraction features. The opticalsubstrate 122 has a front major surface 140 and a back major surface 138arranged generally perpendicular to the optical axis 114. Light isintroduced from the at least one light source 120 between the frontmajor surface 140 and the back major surface 138 (FIGS. 3A-3F and4A-4C). The introduced light is transferred by total internal reflectionthrough the optical substrate 122 between the front major surface 140and back major surface 138 in a direction transverse to the optical axis114. For example, in FIG. 1, light propagates through the opticalsubstrate 122 in a directional generally perpendicular to the opticalaxis 114. In an alternative embodiment depicted in the cross sectionalviews of the optical substrate 122 of FIGS. 3B and 3C, the at least onelight source 120 introduces light into the optical substrate 122 throughthe back major surface 138. In this example, the optical substrate 122has a chamfered surface 125 that reflects light 191 through totalinternal reflection towards the optical axis 114.

As shown in FIG. 1, the front view of the optical substrate 122 shown inFIGS. 2A, and the cross sectional views of the optical substrate 122shown in 3A, and 3D to 3H the at least one light source 120 may bepositioned adjacent an edge 186 of the optical substrate 122. In thisconfiguration, as shown in FIG. 2A, light may exit the at least onelight source 120 through a single light emitting surface (light leavingthe light emitting surface is represented by arrows 190 a-d).

Alternatively, as shown in FIG. 2B the front view of the opticalsubstrate 122 shown in FIG. 2B, and the cross sectional views of theoptical substrate 122 shown in FIGS. 3B and 3C, the at least one lightsource 120 may be positioned on the back major surface 138 at locations121 a-d. In this configuration light may exit the at least one lightsource 120 through a single light emitting surface (light leaving thelight emitting surface) and be reflected from the chamfered edge 125 anddirected towards the optical axis in direction 191.

Alternatively, as shown in FIG. 2C, the at least one light source 120may be positioned within a recess 121 in the optical substrate 122. Inthis example, the at least one light source 120 may emit light frommultiple light emitting surfaces and the light from all of the lightemitting surfaces may enter the optical substrate 122.

Referring briefly to FIG. 2D, the at least one light source 120 may bereduced to four (4) light sources, each of which is arranged on oneexterior edge of the substrate 122 at a location that is not centered onthe edge. For example, light source 120 a may be on a side edge lowerthan center while light source 120 c may be on the opposing side higherthan center. Light source 120 d may be on the top edge to the right ofcenter which light source 120 b may be on the bottom edge to the left ofcenter.

Referring to FIGS. 1 and 2A, the one or more light sources 120 maycomprise multiple LEDs 120 a-d. As will be understood by one of ordinaryskill in the art, the one or more light sources 120 may comprise anysuitable light emitting device. Further, the multiple light sources 120may emit illumination with different characteristics. For example, aportion of the light sources 120 may be white LEDs while another portionmay be red LEDs, or LEDs of another color.

As shown in FIG. 1, the optical substrate 122 may comprise asubstantially flat plate. For example, the optical substrate 122 maycomprise a clear and colorless acrylic substrate which may be made fromany other material suitable for transferring light by total internalreflection. The optical substrate 122 may be positioned within thereader 100 so that a front major surface 140 and a back major surface138 of the optical substrate 122 are located in a plane that issubstantially perpendicular to the optical axis 114. In one embodiment,“substantially perpendicular” means within five degrees of perpendicularwhile in an alternative embodiment substantially perpendicular meanswithin 15 or 20 degrees of perpendicular.

The light emitted from the optical substrate 122 may have differentcharacteristics depending on the characteristics of the opticalsubstrate 122. For example, the optical substrate 122 may utilizerefraction, diffusion, prismatic effect, and/or total internalreflection to direct more diffuse illumination 124 into the field ofview 106. Depending on the properties of the optical substrate 122 andthe at least one light source 120, the illumination system may bereferred to as a diffuse bright field illumination system. The diffusebright field imaging system may also be called a midfield illuminationsystem or a medium field illumination system.

In one embodiment, the light emitted from the optical substrate 122 maybe emitted substantially parallel to the optical axis 114. For example,light may be emitted within 10 degrees of parallel to the optical axis114. Illumination having a smaller angle spread around the optical axis114 may be referred to herein as diffuse bright field illumination 124.

Alternatively, referring to FIGS. 4A to 4C, the optical substrate 122may be shaped such that the shape of the front major surface 140 and/orthe back major surface 138 is concave, convex, parabolic, or somecombination thereof. For example, as shown in FIG. 4A, the opticalsubstrate 122 has a generally concave shape front major surface 140 anda convex shaped back major surface 138, while in FIG. 4B, the opticalsubstrate 122 has a generally convex shape front major surface 140 and aconcave shaped back major surface 138. The shape of at least one of thefront major surface and the back major surface need not be symmetrical,but may be asymmetrical about a plane perpendicular to the optical axis114. In FIG. 4C, the front major surface 140 may include three generallyplanar sections with the central section being generally perpendicularto the optic axis 114 and two generally planar sections adjacent to, andon opposing sides, of the central section being at an angle relative tothe optic axis. In one embodiment the angle may be no greater than 45degrees. In this embodiment the back major surface 138 may also includecorresponding sections with the central section being generallyperpendicular to the optic axis 114 and two generally planar sectionsadjacent to, and on opposing sides, of the central section being at anangle relative to the optic axis. In one embodiment, the angle of thetwo opposing sides of the back major surface 138 may be the same angleas the two opposing sides of the front major surface 140. In anotherembodiment the angle may be different.

The light emitted by the configurations shown FIGS. 4A 4C may be emittedat different angles relative to the optical axis compared to theillumination system 105 depicted in FIG. 1. the illumination system 105with these configurations is a diffuse bright field illumination systemproviding uniform illumination for barcodes applied to a concave/convexsurface.

In embodiments in which the illumination system 105 emits diffuse light,the illumination may be optimal for reading a barcode that has areflective surface that is located in a near zone 158 and/or a centerzone 126 of the field of view 106. The center zone 126 may begin at acenter zone starting boundary 128 and end at a center zone endingboundary 130. The center zone starting boundary 128 is closer to thereader 100 than a far zone starting boundary 118. For example, thecenter zone starting boundary 128 may be located approximately 25 mmaway from the reader 100. The center zone ending boundary 130 may belocated within the far zone 116. Thus, the center zone 126 and the farzone 116 may overlap.

As discussed, the optical substrate 122 may be positioned between theone or more light sources 120. For example, as shown in FIGS. 1, and 2Athe one or more light sources 120 may be located along an edge 186 ofthe optical substrate 122 that is located between the front majorsurface 140 and the back major surface 138. The one or more lightsources 120 introduce light into the edge 186 of the optical substrate.In FIG. 1, light is introduced from the one or more light sources 120into the optical substrate 122 in a direction generally perpendicular tothe optical axis 114 and generally towards the optical axis 114.

For example, as shown in FIG. 3B the one or more light sources 120 maybe located along an edge of the back major surface 138 of the opticalsubstrate 122 with the chamfered edge 125 reflecting illumination in adirection between the front major surface 140 and the back major surface138 in a direction generally perpendicular to the optical axis 114 andgenerally towards the optical axis 114.

The center of the optical substrate 122 may include an opening 133 or anaperture 132 through which objects (such as a barcode) within the fieldof view 106 may be visible to the lens 104 and the photo sensor array102. As shown in FIGS. 2A, 2B, and 2C, the aperture may be rectangularand of sufficient size such that the optical substrate 122 is not withinthe field of view 106 of the camera 103. As shown in FIG. 2E, theoptical substrate 122 may have an approximately annular shape where thecenter opening 133 of the annular optical substrate 122 is circular andof sufficient size such that the optical substrate 122 is not within thefield of view 106 of the camera 103.

With continued reference to FIG. 2C, the optical substrate 122 may havean annular shape that includes an outer edge 186 and an inner edge 187.In the depicted embodiment multiple light sources 120 a-d are positionedon the back major surface 140 of the optical substrate 122 and inputlight into the optical substrate 122 through the back major surface 140.For example, the light sources 120 a-d may be positioned as shown inFIG. 3B or 3C. In FIGS. 3B and 3C, the light sources 120 a-d input lightthrough the back major surface 140 in a direction approximately parallelto the optical axis 114. After entering the optical substrate 122, thelight is reflected by a chamfered surface 125 of the outer edge 186. Thechamfered surface 125 is configured to reflect light onto a pathrelatively perpendicular to the optical axis 114. In another embodiment(not shown) in which the optical substrate has an annular shape, lightenters the optical substrate 122 through the outside edge 186 in adirection approximately perpendicular to the optical axis 114.

To prevent the optical substrate 122 from functioning simply as a lightpipe or light guide, the optical substrate 122 includes one or moreextraction features 142 configured to extract light from the opticalsubstrate 122 and into the field of view 106. The extraction features142 may introduce a variation in the index of refraction (i.e., alocation of non-uniform index of refraction) of the optical substrate122. Each extraction feature 142 functions to disrupt the total internalreflection of the propagating light that is incident on the extractionfeature.

As described above with respect to FIGS. 2A and 2D, the illumination 190a-d directed into the edge 186 of the optical substrate 122 generallypropagates through the optical substrate 122 due to total internalreflection. Any illumination 190 a-d that is incident on the one or moreextraction features 142 may be diffused with a first portion beingdiffused at an angle such that the illumination continues propagatingwithin the optical substrate 122 (based on total internal reflection)and a second portion may be diffused at an angle (i.e., an escape angle)that overcomes total internal reflection, “escapes” the surface, and isdirected into the field of view 106.

The extraction of illumination through the front major surfaceintroduced by the extraction features 142 may comprise at least one of:i) one or more particles within the substrate 122, ii) a planar surfacewithin the optical substrate 122, iii) a variation in the surfacetopography of the back major surface 138, and iv) a variation in thesurface topography of the front major surface 138. For example, in FIGS.3A and 3B, the optical substrate 122 is embedded with particles 142having an index of refraction greater or less than the optical substrate122. As light travels from the edge 186 of the optical substrate 122through total internal reflection towards a center of the opticalsubstrate 122, the particles 142 disrupt the total internal reflectionof the light, causing a portion of the propagating light to exit throughthe front major surface 140.

The extraction features 142 may be configured to extract light in adefined intensity profile over the front major surface 140, such as auniform intensity profile, and/or a defined light ray angledistribution. In FIG. 3A, the one or more extraction features 142 aredistributed non-uniformly throughout the optical substrate 122. In thisexample, the one or more extraction features 142 are distributedthroughout the optical substrate such that light is uniformly emittedfrom the front major surface 140 of the optical substrate 122. Forexample, the extraction features 142 may be spread throughout theoptical substrate 122 in concentrations that increase with distance fromthe at least one light source 120.

Alternatively, in FIG. 3B, the one or more extraction features 142 maybe distributed uniformly or non-uniformly throughout the opticalsubstrate. In this example, the one or more extraction features aredistributed throughout the optical substrate such that light is notuniformly emitted from the front major surface 140 of the opticalsubstrate 122. Instead the light is emitted from the front major surface140 in a desired intensity pattern. While not shown, the one or moreextraction features 142 may be distributed in alternative patterns thatresult in the light being emitted from the front major surface 140 ofthe optical substrate 122 having a more structured appearance (i.e., anon-uniform intensity pattern).

As shown in FIGS. 3C and 3E, the extraction features 142 may alsocomprise a surface variation in the topography of at least one of thefront major surface 140 and the back major surface 138. In the depictedembodiment of FIG. 3C, the one or more extraction features 142 comprisevariations in the back major surface 138 of the optical substrate 122.In this example, the front major surface 140 of the optical substrate122 is smooth and planar, while the back major surface 138 includes atopography of convex and concave indentations and protrusions. In thedepicted embodiment of FIG. 3E, both the back major surface 138 and thefront major surface 140 include extraction features 142 comprisingconvex and concave indentations and protrusions.

These embodiments are configured to result in a homogenous output oflight from the front major surface 140.

The convex and concave indentations and protrusions may be: i) features142 with specific optical properties, such as micro lenses formed by,for example, molding or laser cutting; or ii) features 142 with nospecific optic properties (i.e. random) such as a roughened surfaceformed by any of a textured tool or sanding of the surface aftermolding. Further, the shape, density, or other optical properties of theextraction features 142 may increases with distance from the lightsource 120 a-d in order to produce uniform illumination from the opticalsubstrate.

Turning to FIGS. 3D and 3F, the one or more extraction features 142comprise a surface within the optical substrate 122. In this embodiment,the optical substrate 122 may be made of two different materials 546,548. These materials 546, 548 may have different indices of refraction,and they may be in contact with one another. In FIG. 3E, the contact isalong a surface forming the one or more extraction features 142. In FIG.3F the contact is along a surface of convex and concave shapes, eitherpatterned or random. Refraction at the one or more extraction features142 directs illumination towards the front major surface 140 of theoptical substrate 122 at an angle where the illumination exits the frontmajor surface 140 towards the field of view 106. As a variation to theseembodiments, the materials 546, 548 may have the same index ofrefraction, but a material with a different index of refraction may besandwiched between the materials 546, 548 at the non-planar contactsurface 550.

As will be understood by one of ordinary skill in the art, the opticalsubstrate 122 and the extraction features 142 are not limited to thesedescribed embodiments. Other embodiments of the optical substrate 122including extraction features 142 are also within the scope of thepresent disclosure.

In all of these embodiments, to further increase the quantity ofillumination exiting through the front major surface 140, a reflectivebacking 144 may be applied to the back major surface 138. The reflectivebacking 144 may be applied uniformly such that it covers the entire backmajor surface 138. The reflective backing 144 reduces the amount oflight that escapes through the back major surface 138 by reflectinglight back inward into the optical substrate 122. In another embodiment,a cladding film (not shown) having an index of refraction less than theindex of refraction of the optical substrate 122 is adjacent the backmajor surface 138. The cladding film reduces the amount of light thatescapes by reflecting light inward through total internal reflection.Similarly, all edges and surfaces of the optical substrate 122 (exceptfor the edges 186 where the one or more light sources 120 a-d projectillumination into the optical substrate 122) may also be coated with areflective backing 144.

Depending on the properties of the illumination system 105, the lightemitted by the illumination system 105 from the one or more lightsources 120 may not be sufficiently bright to provide optimalillumination for reading a barcode that is located farther away from thereader 100 than the center zone ending boundary 130. For this reason, asshown in FIG. 1, the illumination system may comprise at least onesecondary light source 108. The at least one secondary light source 108may be referred to as a direct bright field illumination system or a farfield illumination system. Light from the at least one secondary lightsource 108 that is emitted by the illumination system 105 may convergeat a point on the optical axis 114 that is different from the pointalong the optical axis 114 that light from the at least one light source120 converges. For example, the light may be emitted by the illuminationsystem 105 at an angle closer to parallel to the optical axis 114, forexample at a convergence angle of approximately 70 degrees) than thelight from the at least one light source 120 that is emitted by theillumination system 105.

The at least one secondary light source may comprise one or more LEDs108 a-b, which may be positioned behind refracting and/or diffusingoptics 110 a-b. The one or more secondary light sources 108 a-b maydirect illumination 112 into the field of view 106 substantiallyparallel to the optical axis 114 but with a slight convergence angle.For example, the one or more secondary light sources 108 a-d may directillumination into the field of view 106 at an angle from 0-30 degreesfrom the optical axis 114. This illumination 112 may be referred toherein as direct bright field illumination 112 or far fieldillumination. As indicated above, the optical axis 114 is a lineoriginating from the center of the focusing lens 104 and extendingoutward into the center of the field of view 106.

Light emitted by the illumination system from the at least one secondarylight source may be better suited for reading a barcode with a diffusesurface such as a paper label. Light emitted by the illumination systemfrom the at least one secondary light source may also be optimal forreading a barcode that is located in a far zone 116 of the field of view106, i.e., an area of the field of view 106 that is relatively far awayfrom the reader 100. In other words, light from the at least onesecondary light source may have sufficient intensity to illuminate abarcode that is located within the far zone 116. The far zone 116 maybegin at a far zone starting boundary 118 and end at a far zone endingboundary 119. In one implementation, the far zone starting boundary 118may be located about 75 mm away from the reader 100. The bright fieldillumination 112 may not be sufficiently diffuse to provide optimalillumination for reading a barcode that has a reflective surface. Forlonger range reading, the illumination system may additionally comprisea focus lens associated with the at least one secondary light source inorder to provide illumination for reading a barcode that is locatedfarther away from the reader 100 than the far zone ending boundary 119.

The optical substrate 122 may further include apertures 134 a-b thatpermit the direct bright field illumination 112 (from the at least onesecondary light source 108 a-b) to be directed into the field of view106 without being affected by the optical substrate 122. Further yet,the optical substrate 122 may include apertures 136 a-b that permittargeting illumination from targeting light sources 109 a-b (FIG. 1)mounted behind the optical substrate 122 to be projected into the fieldof view 106 without being affected by the optical substrate 122.

The secondary light source may include secondary light sources 108 a,108 b mounted within the housing 101. Secondary light sources 108 a, 108b are the interior of the housing 101 and may be behind tertiary lightsources 152 a-b (discussed herein) which are behind diffusors 154 a, 154b. The secondary light sources 108 a, 108 b may be in front of thetertiary light sources 152 a, 152 b. As will be discussed with respectto FIG. 6, the secondary light sources may also be positioned in frontof the illumination sources 120 a, 120 b but behind the tertiary lightsources 152 a-b.

The surfaces of the apertures 132, 134 a-b, 136 a-b within the opticalsubstrate 122 may be coated with an opaque reflective material (notshown). This material may cause illumination within the opticalsubstrate 122 that is incident on the surface of a particular apertureto be reflected back into the optical substrate 122 regardless of itsangle of incidence. Reflecting illumination back into the opticalsubstrate 122 prevents illumination from exiting the optical substrate122 through the surface of any aperture at an angle where it wouldilluminate the region behind the optical substrate 122, such as directlyilluminating the lens 104 and degrading the quality of the image of anobject within the field of view 106.

Referring again to FIG. 1, the illumination system 105 may also includeat least one tertiary light source 152. Light from the at least onetertiary light source 152 may be emitted by the illumination system 105at an angle closer to perpendicular to the optical axis 114 than thelight from either of the at least one light source 120 or the at leastone secondary light source 108 that is emitted by the illuminationsystem 105. The at least one tertiary light source 152 may comprisemultiple LEDs 152 a-b. Additional optics 154 a-b may also be associatedwith the at least one tertiary light source 152 to direct illuminationto the field of view 106. The additional optics 154 a-b may utilizerefraction, diffusion, prismatic effect, and/or total internalreflection to direct illumination 156 a-b into the field of view 106.

The at least one tertiary light source 152 may be referred to as a darkfield illumination system or a near field illumination system. Lightemitted by the illumination system from the at least one tertiary lightsource may be referred to herein as dark field illumination 156 a-b.Light from the at least one tertiary light source may be emitted by theillumination system (i.e., the dark field illumination 156 a-b) at anangle no more than 45° from a plane perpendicular to the optical axis114.

The dark field illumination 156 a-b may be optimal for reading a barcodethat is located within a close zone 158 of the field of view 106. Theclose zone 158 may begin at a close zone starting boundary 160 and mayend at a close zone ending boundary 162. The close zone startingboundary 160 may be closer to the reader 100 than the center zonestarting boundary 128. The close zone starting boundary 160 maycorrespond to the face of the reader 100. The close zone ending boundary162 may be within the center zone 126. Thus, the close zone 158 and thecenter zone 126 may overlap. However, the dark field illumination 156a-b may not be sufficiently bright to provide optimal illumination forreading a barcode that is located farther away from the reader 100 thanthe close zone ending boundary 162.

In the embodiment shown in FIG. 1, the at least one tertiary lightsource 152 a-b is mounted on circuit boards at the sides of the readerhousing 101. The optics 154 a-b may comprise lenses, gratings, ordiffusion material that diffuses the illumination 156 a-b from the atleast one tertiary light source 152.

With reference to FIG. 5, an alternative embodiment of the barcodereader 100 is depicted. In this embodiment, the at least one tertiarylight source 152 a-b is mounted on a circuit board 792 that issubstantially perpendicular to the optical axis 114. Illumination 776a-b from the at least one tertiary light sources 152 a-b is directedsubstantially parallel to the optical axis 114 toward prism optics 778a-b. More specifically, the at least one tertiary light source 152 a-bmay project illumination 776 a-b into light pipes 788 a-b, which usetotal internal reflection to propagate the illumination 776 a-b towardthe prism optics 778 a-b. The prism optics 778 a-b are used to re-directthe illumination 776 a-b toward the field of view 106 at the desiredangle.

The light pipes 788 a-b may comprise chamfered ends 778 a-b. Thesechamfered ends 778 a-b may serve as the prism optics 778 a-b thatre-direct the illumination 776 a-b toward the field of view 706. Each ofthe chamfered ends 778 a-b may be angled such that total internalreflection redirects the illumination 776 a-b at a non-zero angle (e.g.,45°) relative to the plane that is perpendicular to the optical axis714. The illumination 776 a-b may exit the light pipes 788 a-b throughthe side facing the optical axis 714. It should be appreciated that thelight pipes 778 a-778 b are shown in cross section and may be on eachside of the camera (all four sides, left, right, top, bottom) or mayeven form an annular ring around the field of view of the camera.

Turning to FIG. 6, another embodiment of the barcode reader 100 isshown. In this embodiment, the optical substrate 880 forms a protectivewindow over optical substrate 122 and replaces the optics 110 a-b, and154 a-b of FIG. 1. In this example, the at least one tertiary lightsource 152 comprise LEDs 152 a-b positioned behind diffusion regions 884a-b of the optical substrate 880. The diffusion regions 884 a-b directdark field illumination 856 a-b from the LEDs 152 a-b into the field ofview 806. The curved regions 882 a-b provide structural support for thediffusion regions 884 a-b as well as focusing the illumination projectedfrom secondary illumination sources 108 a, 108 b—or secondaryillumination sources 115 a, 115 b.

Turning to FIG. 7, another embodiment of the barcode reader 100 isshown. In this embodiment, the optical substrate 881 forms a protectivewindow over optical substrate 122 and replaces the optics 110 a-b ofFIG. 1.

As shown in FIG. 8A, the illuminators 884 may include an opticalsubstrate into which illumination 815 a-b is projected by two side fireilluminators 813 a-b. The illumination 815 a-b is internally reflectedwithin the substrate 811 and extracted as diffuse illumination 156 fromthe optical substrate 811. The optical substrate 811 may have any of thecharacteristics, and extraction features, as the optical substrate 122as described with respect to FIGS. 1, 2A-D, 3A-F, and 4A-C, as well asreflective coatings such that illumination propagates between a frontmajor surface and aback major surface of optic 811 and it extractedthrough the front major surface as illumination 156.

As shown in FIG. 8B, the illuminators 884 may include an opticalsubstrate 821 into which illumination 825 a-b is projected through theback major surface by two illuminators 819 a-b. The illumination 825 a-bis reflected from chamfered surfaces such that it propagates between thefront major surface and the back major surface and is extracted asdiffuse illumination 156 from the optical substrate 821. As with opticalsubstrate 811, the optical substrate 821 may have any of thecharacteristics, and extraction features, as the optical substrate 122as described with respect to FIGS. 1, 2A-D, 3A-F, and 4A-C, as well asreflective coatings such that illumination propagates between a frontmajor surface and aback major surface of optic 811 and it extractedthrough the front major surface as illumination 156.

The diffusion regions 884 a-b direct dark field illumination 856 a-bfrom the LEDs into the field of view 806. The curved regions 882 a-bprovide structural support for and focusing the illumination projectedfrom secondary illumination sources 108 a, 108 b—or secondaryillumination sources 115 a, 115 b. Posts 883 a and 883 b providestructural support for the dark field illumination systems 884 a-b andprevent illumination from entering into the curved regions 882 a-b.

The previous discussion has been directed to a barcode reader thatincludes three different light sources: at least one secondary lightsource (a bright field illumination system—positioned at any of: i)closer to the field of view (i.e. in front of) than the tertiary lightsources, ii) behind the tertiary light sources but in front of thediffuse bright field illumination sources; or iii) behind the diffusebright field illumination sources and optical substrate 122), at leastone light source (a diffuse bright field illumination system), and atleast one tertiary light source (a dark field illumination system).

It should also be appreciated that each of these illumination sourcesmay generate illumination with different characteristics. For example,the diffuse bright field illumination may be white LEDs (illuminationwith intensity across a wide spectrum of wave lengths) while thetertiary light source and the secondary light source may be red LEDs(i.e. intensity at 660 nm).

These three illumination systems can be independently operated such thata barcode can be read with the illumination system that provides thebest illumination for reading the barcode. The discussion that followsincludes some examples of how this may be accomplished. Although some ofthese examples involve only two different illumination systems, thoseexamples may be extended to barcode readers that include three (or more)different illumination systems.

Photo sensor arrays can be operated in two modes: a rolling shutter modeof operation and a global shutter mode of operation. In the globalshutter mode of operation, all photo sensors within the array (i.e., allrows of the array) may be exposed at the same time for the duration ofan exposure period. During the exposure period charge may accumulate oneach photo sensor based on the incident illumination. At the end of theexposure period the charge may be read out row by row.

In the rolling shutter mode of operation, two different signals may beutilized: a reset signal and a read signal. The reset signal may affectall of the photo sensors in a row and may put the photo sensors in astate to convert light intensity into an electrical signal. The readsignal may similarly be applied to all of the photo sensors in a row,and may cause the electrical signals from each photo sensor in the rowto be read electronically.

To capture an image, the reset signal may be applied sequentially toeach row in the photo sensor array, starting at the top of the photosensor array and proceeding row-by-row to the bottom of the photo sensorarray. At some fixed time interval after this reset process has started,the readout process may begin, i.e., the read signal may be appliedsequentially to each row in the photo sensor array. The “exposure” of arow of photo sensors refers to the period of time between the row ofphoto sensors being reset and the row of photo sensors being read.

The exposure time may be expressed as an integer value. The actualexposure time may be the integer value multiplied by the duration oftime required to read out a single row. As such, the size of the rolling“exposure zone” may be the quantity of lines represented by the integervalue. For example, if the exposure value is 10, when exposure of row 1is complete and read out of row 1 starts, row 11 would start exposureand be exposed for the duration of read out of rows 1 to 10.

In both the global shutter mode of operation and the rolling shuttermode of operation, windowing may be utilized. When windowing isutilized, only a portion of the photo sensor array (typically ahorizontal window) is used for exposure and read out. Because only aportion of the photo sensor array is used for exposure, imaging abarcode using windowing is faster than using the entire photo sensorarray. For example, for the global shutter mode a window of 128 rowsbetween rows 128 and 256 may be simultaneously exposed for an exposureduration, and the accumulated charge may be read out row by row. In thisexample, there is no read out of rows below 128 or above 256. In therolling shutter mode, a window of 128 rows between rows 128 and 256 maybe exposed and read out using a rolling exposure zone as discussedabove. Again there would not be any read out of rows below 128 or above256.

As indicated above, the present disclosure relates generally totechniques for selecting the type of illumination that will be mostsuitable for reading a barcode in a particular situation. FIG. 9illustrates one configuration of a barcode reader 902 in accordance withthe present disclosure.

The barcode reader 902 includes a photo sensor array 904. The photosensor array 904 may be capable of operating in accordance with a globalshutter mode of operation and/or a rolling shutter mode of operation, asdiscussed above. The photo sensor array 904 may also be capable ofutilizing windowing, as discussed above.

The barcode reader 902 also includes a plurality of illumination systems906 a-b having different illumination characteristics. Some examples ofdifferent illumination characteristics include the angle of illuminationwith respect to an optical axis, the intensity of illumination, thewavelength of illumination, diffusion characteristics of theillumination, etc.

The plurality of illumination systems 906 may include a bright fieldillumination system 906 a and a dark field illumination system 906 b.The bright field illumination system 906 a may provide illuminationhaving characteristics designed to illuminate a target area that islocated relatively far away from the reader 902. Conversely, the darkfield illumination system 906 b may provide illumination havingcharacteristics designed to illuminate a target area that is locatedrelatively close to the reader 902.

Of course, the number of illumination systems 906 a-b shown in FIG. 9 isfor purposes of example only. In an alternative configuration, a barcodereader may include more than two different illumination systems.Alternatively still, a barcode reader in accordance with the presentdisclosure may include a single illumination system that is configuredto provide illumination having different illumination characteristics(e.g., by changing the intensity, wavelength, angle, and/or diffusioncharacteristics of the illumination).

The barcode reader 902 also includes illumination selection circuitry908. The illumination selection circuitry 908 may be configured toperform operations that are related to selecting the type ofillumination that will be most suitable for reading a barcode in aparticular situation.

FIG. 10 illustrates an example of a method 1000 that may be performed bythe illumination selection circuitry 908 in accordance with the presentdisclosure. The circuitry 908 may be configured to cause the photosensor array 904 to capture 1002 at least one test image. For example,the photo sensor array 904 may capture 1002 a single test image 1210(see, e.g., FIGS. 11 and 12). Alternatively, the photo sensor array 904may capture 1002 a plurality of test images 1210 a-b (see, e.g., FIGS.13, 14A and 14B).

The photo sensor array 904 may utilize windowing when the test image(s)are captured 1002, so that the test image(s) may each be smaller than afull photo sensor array image. As used herein, the term “full photosensor array image” refers to an image that is captured when an entirephoto sensor array 904 is exposed and read out. Thus, a full photosensor array image may include pixels corresponding to all of the photosensors in the photo sensor array 904. In contrast, the test image(s)may each include pixels corresponding to only a subset (i.e., less thanall) of the photo sensors in the photo sensor array 904. Capturing atest image that includes pixels corresponding to only a subset of thephoto sensors in the photo sensor array 904 takes less time thancapturing a full photo sensor array image.

The test image(s) may include at least a portion of a barcode. That is,only a portion of a barcode (i.e., less than an entire barcode) may bevisible in the test image(s). Alternatively, an entire barcode may bevisible in the test image(s).

The test image(s) may include a plurality of window images. As usedherein, the term “window image” refers to an image that is smaller thana full photo sensor array image. In one possible configuration, a singletest image 1210 may be captured, and the single test image 1210 maycomprise a plurality of window images 1212 a-b. (See, e.g., FIG. 12.) Inanother possible configuration, a plurality of test images 1410 a-b maybe captured, and each test image 1410 may comprise a window image 1412.(See, e.g., FIGS. 14A-14B.)

Returning to FIG. 10, the circuitry 908 may be configured to provide1004 illumination for each window image from a distinct configuration ofthe plurality of illumination systems 906 a-b. For example, if thebarcode reader 902 includes a bright field illumination system 906 a anda dark field illumination system 906 b, the test image(s) may include atleast two different window images. The illumination for capturing afirst window image may be provided solely by the bright fieldillumination system 906 a, and the illumination for capturing a secondwindow image may be provided solely by the dark field illuminationsystem 906 b.

Alternatively, multiple illumination systems 906 a-b may be activated atthe same time with various permutations of balanced intensity. Forexample, the illumination for capturing the first window image may beprovided by the bright field illumination system 906 a at 60% power andthe dark field illumination system 906 b at 40% power. The illuminationfor capturing the second window image may be provided by the brightfield illumination system 906 a at 40% power and the dark fieldillumination system 906 b at 60% power.

The circuitry 908 may also be configured to determine 1006 a selectedillumination system configuration. The selected illumination systemconfiguration may be a configuration of the plurality of illuminationsystems 906 a-b that yielded a window image having highest quality amongthe plurality of window images.

Generally speaking, the quality of an image of a barcode may be measuredin terms of the contrast between the light cells and the dark cellswithin the barcode. A barcode image having relatively high contrastbetween dark cells and light cells may be considered to have higherquality than another barcode image having relatively low contrastbetween dark cells and light cells.

The terms “dark cells” and “light cells” are used herein becausebarcodes have traditionally been printed with ink. This gives barcodesthe appearance of having dark cells (the portion that is printed withink) and light cells (the unprinted substrate background, typicallywhite). However, with direct part mark technology, ink is not alwaysused and other techniques (e.g., laser/chemical etching and/or dotpeening) may be used instead. Such techniques may be utilized to createa barcode by causing different portions of a substrate to have differentreflective characteristics. When these different portions of thesubstrate are imaged, the resulting barcode image may have theappearance of including dark cells and light cells. Therefore, as usedherein, the terms “dark cells” and “light cells” should be interpretedas applying to barcodes that are printed with ink as well as barcodesthat are created using other technologies.

The contrast between the dark cells and the light cells in a barcode maybe a function of illumination. Ideally, it is desirable to provideillumination that is consistent across the barcode and of an intensitysuch that the exposure of the image yields both dark cells and lightcells that are within the dynamic range of the photo sensor array 904.This yields better contrast than any of the following: (i) a dimly litbarcode; (ii) a brightly lit barcode wherein the image is washed outbeyond the dynamic range of the photo sensor array 904; (iii) anunevenly lit barcode with bright washed out spots; or (iv) a barcodeilluminated with illumination that is not compatible with thereflectivity characteristic(s) of the cells of the barcode. An exampleof (iv) is that illumination directed from the sides of the field ofview yields a higher contrast image of a barcode formed by etchingtechnology than does illumination parallel to the optical axis.

If the quality of a window image is measured in terms of contrast,determining 1006 the selected illumination system configuration mayinclude determining which window image of the plurality of window imageshas highest contrast between light and dark cells of the barcode, anddetermining which configuration of the plurality of illumination systems906 a-b was activated when the window image having the highest contrastwas captured.

Alternatively, the quality of the window images may be measured in termsof the presence of desired barcode features and/or patterns. A score ormetric may be calculated for each window image. A particular windowimage's score/metric may indicate the number of desired barcode featuresand/or patterns that are detected in the window image. For example, ahigher score/metric may indicate a greater number of desired barcodefeatures and/or patterns (or vice versa). If the quality of the windowimages is measured in this way, then determining 1006 the selectedillumination system configuration may include determining which windowimage of the plurality of window images has the most favorablescore/metric based on features or patterns of the barcode, anddetermining which configuration of the plurality of illumination systems906 a-b was activated when the window image having the most favorablescore/metric was captured.

The circuitry 908 may also be configured to cause the photo sensor array904 to capture 1008 a subsequent image using the selected illuminationsystem configuration. The subsequent image may be captured using aglobal shutter or a rolling shutter mode of operation. As indicatedabove, the test image(s) may include only a portion of a barcode (i.e.,only part of the barcode may be visible within the test image(s)).However, the subsequent image may include an entire barcode (i.e., theentire barcode may be visible within the subsequent image).

The subsequent image may be a full photo sensor array image. That is,the subsequent image may include pixels corresponding to all of thephoto sensors in the photo sensor array 904. Alternatively, thesubsequent image may include pixels corresponding to substantially allof the photo sensors in the photo sensor array 904. In this context, thephrase “substantially all” of the photo sensors in the photo sensorarray 904 may mean at least 95% of the photo sensors in the photo sensorarray 904.

Alternatively still, the size of the subsequent image may be larger thanthe test image(s), but less than a full photo sensor array image. Forexample, referring to FIG. 10A, a test image 1010 may include pixelscorresponding to a first subset 1018 of the photo sensors in the photosensor array 904, and the subsequent image 1016 may include pixelscorresponding to a second subset 1020 of the photo sensors in the photosensor array 904. The second subset 1020 may be larger than the firstsubset 1018. However, the second subset 1020 may not include all of thephoto sensors in the photo sensor array 904.

The size and location of the second subset 1020 may be determined basedon defined rules. For example, the size and location of the secondsubset 1020 may correspond to the size and location of a previously readbarcode. Alternatively, the size and location of the second subset 1020may be determined by estimating the border of the barcode 1022 in thetest image 1010 based on characteristics of the barcode 1022 visible inthe test image 1010, and then setting the size and location of thesecond subset 1020 to include the estimated border.

As another example, if the dark field illumination system 906 b yields ahigher quality window image than the bright field illumination system906 a, then the entire photo sensor array 904 may be utilized to capturethe subsequent image 1016 (because the “up close” barcode 1022 will belarger). Conversely, if the bright field illumination system 906 ayields a higher quality window image than the dark field illuminationsystem 906 b, then a subset 1020 (e.g., a central portion) of the photosensors within the photo sensor array 904 may be utilized to capture thesubsequent image 1016 (because the “far away” barcode 1022 will besmaller).

FIG. 11 illustrates another example of a method 1100 that may beperformed by the illumination selection circuitry 908 in accordance withthe present disclosure. The circuitry 908 may be configured to cause thephoto sensor array 904 to capture 1102 a single test image 1210 (shownin FIG. 12) of at least a portion of a barcode using a rolling shuttermode of operation. Windowing may be utilized, so that the test image1210 may be smaller than a full photo sensor array image.

The circuitry 908 may be configured to cycle through 1104 a plurality ofconfigurations of the plurality of illumination systems 906 a-b whilethe test image 1210 is being captured, so that each illumination systemconfiguration is activated for a distinct time period while the testimage 1210 is being captured and is not otherwise activated while thetest image 1210 is being captured. Consequently, the test image 1210 mayinclude a plurality of window images 1212 a-b. Each window image 1212may correspond to a distinct band (e.g., a horizontal band) within thetest image 1210, and each window image 1212 may correspond to a distinctillumination system configuration.

For example, during exposure of a first section 1214 a of the photosensor array 904, the bright field illumination system 906 a may beactivated, while the dark field illumination system 906 b may bedeactivated. During exposure of a second section 1214 b of the photosensor array 904, the dark field illumination system 906 b may beactivated, while the bright field illumination system 906 a may bedeactivated. (Both the bright field illumination system 906 a and thedark field illumination system 906 b may be activated during exposure ofthe section of the photo sensor array 904 between the first section 1214a and the second section 1214 b, as the transition is made from onesystem to the other.)

In this example, the test image 1210 that is captured includes twodistinct bands. The band corresponding to the first section 1214 a ofthe photo sensor array 904 is captured using illumination solely fromthe bright field illumination system 906 a. Thus, this window image 1212a may indicate the suitability of the bright field illumination system906 a for capturing an image of a barcode. The band corresponding to thesecond section 1214 b of the photo sensor array 904 is captured usingillumination solely from the dark field illumination system 906 b. Thus,this window image 1212 b may indicate the suitability of the dark fieldillumination system 906 b for capturing a barcode.

In the example just described, there is one window image 1212 for eachillumination system 906. However, under some circumstances multiplewindow images may be captured for one or more of the illuminationsystems 906. For example, during exposure of a first section of thephoto sensor array 904, the bright field illumination system 906 a maybe activated, while the dark field illumination system 906 b may bedeactivated. During exposure of a second section of the photo sensorarray 904, the dark field illumination system 906 b may be activated,while the bright field illumination system 906 a may be deactivated.During exposure of a third section of the photo sensor array 904, thebright field illumination system 906 a may be activated at reduced power(e.g., 50%), while the dark field illumination system 906 b may bedeactivated. The test image in this example may include three windowimages corresponding to three distinct bands within the test image. Thefirst window image may indicate the suitability of the bright fieldillumination system 906 a for capturing an image of a barcode. Thesecond window image may indicate the suitability of the dark fieldillumination system 906 b for capturing an image of a barcode. The thirdwindow image may indicate the suitability of the bright fieldillumination system 906 a, operating at reduced power, for capturing animage of a barcode.

Alternatively, both illumination systems 906 a-b may be activated at thesame time with various permutations of balanced intensity. For example,the band corresponding to the first section 1214 a of the photo sensorarray 904 may be captured using illumination from the bright fieldillumination system 906 a powered at 60% and the dark field illuminationsystem 906 b powered at 40%. The band corresponding to the secondsection 1214 b of the photo sensor array 904 may be captured usingillumination from the bright field illumination system 906 a powered at40% and the dark field illumination system 906 b powered at 60%.

In FIG. 12, the width of the test image 1210 and the width of the windowimages 1212 a, 1212 b within the test image 1210 are shown as beingequal to the width of the photo sensor array 904. As shown in FIG. 12A,however, the width of the test image 1210′ and the width of the windowimages 1212 a′, 1212 b′ within the test image 1210′ may alternatively beless than the width of the photo sensor array 904.

Returning to FIG. 11, the circuitry 908 may also be configured todetermine 1106 a selected configuration of the plurality of illuminationsystems 906 a-b. The selected illumination system configuration may bethe configuration of the plurality of illumination systems 906 a-b thatyielded a window image 1212 having highest quality among the pluralityof window images 1212 a-b. The circuitry 908 may also be configured tocause the photo sensor array 904 to capture 1108 a subsequent imageusing the selected illumination system configuration.

FIG. 13 illustrates another example of a method 1300 that may beperformed by the illumination selection circuitry 908 in accordance withthe present disclosure. The circuitry 908 may be configured to cause thephoto sensor array 904 to capture 1302 a plurality of test images 1410a-b (shown in FIGS. 14A-6B) of at least a portion of a barcode. Theplurality of test images 1410 a-b may be captured 1302 using a rollingshutter mode of operation or using a global shutter mode of operation.As shown in FIG. 14A, the plurality of test images 1410 a-b maycorrespond to different sections of the photo sensor array 904. In otherwords, a first section of the photo sensor array 904 may be exposed andread out in order to capture the first test image 1410 a, and a secondsection of the photo sensor array 904 may be exposed and read out inorder to capture the second test image 1410 b. Alternatively, as shownin FIG. 14B, the plurality of test images 1410 a-b may correspond to thesame section of the photo sensor array 904. In other words, the samesection of the photo sensor array 904 may be exposed and read out inorder to capture both test images 1410 a-b.

The circuitry 908 may be configured to cycle through 1304 a plurality ofconfigurations of the plurality of illumination systems 906 a-b whilethe plurality of test images 1410 a-b are being captured, so that eachillumination system configuration is used as the sole source ofillumination for at least one test image 1410. Each test image 1410 maytherefore be considered to be a window image 1412 corresponding to aparticular illumination system configuration. In other words, theplurality of test images 1410 a-b may comprise a plurality of windowimages 1412 a-b. Each window image 1412 may correspond to a differentone of the plurality of test images 1410 a-b. Each window image 1412 mayalso correspond to a different one of the plurality of illuminationsystem configurations.

For example, a first test image 1410 a and a second test image 1410 bmay be captured. The bright field illumination system 906 a may beactivated and the dark field illumination system 906 b may bedeactivated while the first test image 1410 a is being captured.Conversely, the dark field illumination system 906 b may be activatedand the bright field illumination system 906 a may be deactivated whilethe second test image 1410 b is being captured. The first test image1410 a may be considered to be a window image 1412 a corresponding tothe bright field illumination system 906 a. The second test image 1410 bmay be considered to be a window image 1412 b corresponding to the darkfield illumination system 906 b.

Alternatively, the bright field illumination system 906 a may beactivated at 60% power and the dark field illumination system 906 b maybe activated at 40% power while the first test image 1410 a is beingcaptured. The bright field illumination system 906 a may be activated at40% power and the dark field illumination system 906 b may be activatedat 60% power while the second test image 1410 b is being captured.

Returning to FIG. 13, the circuitry 908 may also be configured todetermine 1306 a selected illumination system configuration. Theselected illumination system configuration may be the configuration ofthe plurality of illumination systems 906 a-b that yielded a windowimage 1412 having highest quality among the plurality of window images1412 a-b. The circuitry 908 may also be configured to cause the photosensor array 904 to capture 1308 a subsequent image using the selectedillumination system configuration.

In the examples that are shown in FIGS. 14A and 14B, the width of thetest images 1410 a-b and window images 1412 a-b are equal to the widthof the photo sensor array 904. Alternatively, however, the width of thetest images and window images may be less than the width of the photosensor array 904.

FIG. 15 illustrates another example of a method 1500 that may beperformed by the illumination selection circuitry 908 in accordance withthe present disclosure. The illumination selection circuitry 908 may beconfigured to cause the photo sensor array 904 to capture 1502, usingone or more test images, a plurality of window images of at least aportion of a barcode.

The plurality of window images may include a first window image and asecond window image. The illumination selection circuitry 908 may beconfigured to provide 1504 illumination having a first set ofillumination characteristics for capturing the first window image andillumination having a second set of illumination characteristics(different than the first set of illumination characteristics) forcapturing the second window image. In this context, a “set ofillumination characteristics” may include multiple illuminationcharacteristics, or only a single illumination characteristic. Someexamples of different illumination characteristics were described above.

Different illumination systems 906 a-b may be utilized to provideillumination having different illumination characteristics.Alternatively, a single illumination system 906 may be utilized, but theillumination system may be capable of providing illumination havingdifferent illumination characteristics.

The illumination selection circuitry 908 may also be configured todetermine 1606 a selected set of illumination characteristics. Theselected set of illumination characteristics may be the set ofillumination characteristics that yielded a window image having highestquality among the plurality of window images.

As indicated above, the quality of a window image may be measured interms of image contrast. Therefore, determining 1506 the selected set ofillumination characteristics may include determining which window imageof the plurality of window images has highest contrast between light anddark cells of the barcode, and determining which set of illuminationcharacteristics was utilized when the window image having the highestcontrast was captured.

Alternatively, as indicated above, the quality of a window image may bemeasured in terms of the presence of desired barcode features and/orpatterns. Therefore, determining 1506 the selected set of illuminationcharacteristics may include determining which window image of theplurality of window images has the most favorable score/metric based onfeatures or patterns of the barcode, and determining which set ofillumination characteristics was utilized when the window image havingthe most favorable score/metric was captured.

The illumination selection circuitry 908 may also be configured to causethe photo sensor array 904 to capture 1508 a subsequent image using theselected set of illumination characteristics. The subsequent image maybe captured using a global shutter or a rolling shutter mode ofoperation. As indicated above, the test image(s) may include only aportion of a barcode. However, the subsequent image may include anentire barcode.

FIG. 16 illustrates another example of a method 1600 that may beperformed by the illumination selection circuitry 908 in accordance withthe present disclosure. The illumination selection circuitry 908 may beconfigured to cause the photo sensor array 904 to capture 1602 a singletest image 1210 of at least a portion of a barcode using a rollingshutter mode of operation. Windowing may be utilized, so that the testimage 1210 may be smaller than a full photo sensor array image.

The circuitry 908 may be configured to cycle 1604 through a plurality ofsets of illumination characteristics while the test image 1210 is beingcaptured, so that each set of illumination characteristics is utilizedfor a distinct time period while the single test image 1210 is beingcaptured and is not otherwise utilized while the single test image 1210is being captured. Consequently, the test image 1210 may include aplurality of window images 1212 a-b, where each window image 1212corresponds to a distinct band within the test image 1210, and whereeach window image 1212 corresponds to a distinct one of the plurality ofsets of illumination characteristics.

For example, during exposure of a first section 1214 a of the photosensor array 904, a first set of illumination characteristics (e.g.,direct, high intensity illumination) may be utilized. The window image1212 a may correspond to this first set of illumination characteristics.During exposure of a second section 1214 b of the photo sensor array904, a second set of illumination characteristics (e.g., angled, lowintensity, diffuse illumination) may be utilized. The window image 1212b may correspond to this second set of illumination characteristics.

Alternatively, during exposure of the first section 1214 a of the photosensor array 904, both the bright field illumination system 906 a andthe dark field illumination system 906 b may be activated, with thebright field illumination system 906 a powered at 60% and the dark fieldillumination system 906 b powered at 40%. During exposure of the secondsection 1214 b of the photo sensor array 904, both the bright fieldillumination system 906 a and the dark field illumination system 906 bmay be activated, with the bright field illumination system 906 apowered at 40% and the dark field illumination system 906 b powered at60%.

The circuitry 908 may also be configured to determine 1606 a selectedset of illumination characteristics. The selected set of illuminationcharacteristics may be the set of illumination characteristics thatyielded a window image 1212 having highest quality among the pluralityof window images 1212 a-b. The circuitry 908 may also be configured tocause the photo sensor array 904 to capture 1608 a subsequent imageusing the selected set of illumination characteristics.

FIG. 17 illustrates another example of a method 1700 that may beperformed by the illumination selection circuitry 908 in accordance withthe present disclosure. The circuitry 908 may be configured to cause thephoto sensor array 904 to capture 1702 a plurality of test images 1410a-b of at least a portion of a barcode. The plurality of test images1410 a-b may be captured using a rolling shutter mode of operation orusing a global shutter mode of operation. The plurality of test imagesmay correspond to different sections of the photo sensor array 904 (asshown in FIG. 14A), or to the same section of the photo sensor array 904(as shown in FIG. 14B).

The circuitry 908 may be configured to cycle 1704 through a plurality ofsets of illumination characteristics while the plurality of test images1410 a-b are being captured, so that each set of illuminationcharacteristics is used as the sole source of illumination for at leastone test image 1410. Each test image 1410 may therefore be considered tobe a window image 1412 corresponding to a particular set of illuminationcharacteristics. In other words, the plurality of test images 1410 a-bmay include a plurality of window images 1412 a-b, where each windowimage 1412 may correspond to a different one of the plurality of testimages 1410 a-b, and where each window image 1412 may correspond to adifferent one of the plurality of sets of illumination characteristics.

The circuitry 908 may also be configured to determine 1706 a selectedset of illumination characteristics. The selected set of illuminationcharacteristics may be the set of illumination characteristics thatyielded a window image having highest quality among the plurality ofwindow images. The circuitry 908 may also be configured to cause thephoto sensor array 904 to capture 1708 a subsequent image using theselected set of illumination characteristics.

FIG. 18 illustrates various components that may be utilized in a barcodereader 1802. Any of the barcode readers 100, 700, 800, 902 describedpreviously may include some or all of the components of the barcodereader 1802.

The barcode reader 1802 includes a processor 1804. The processor 1804may be a general purpose single- or multi-chip microprocessor (e.g., anARM), a special purpose microprocessor (e.g., a digital signal processor(DSP)), a microcontroller, a programmable gate array, etc. The processor1804 may be referred to as a central processing unit (CPU). Althoughjust a single processor 1804 is shown in the barcode reader 1802 of FIG.18, in an alternative configuration, a combination of processors (e.g.,an ARM and DSP) could be used.

The barcode reader 1802 also includes memory 1806 in electroniccommunication with the processor 1804. That is, the processor 1804 canread information from and/or write information to the memory 1806. Thememory 1806 may be any electronic component capable of storingelectronic information. The memory 1806 may be random access memory(RAM), read-only memory (ROM), magnetic disk storage media, opticalstorage media, flash memory devices in RAM, on-board memory includedwith the processor 1804, programmable read-only memory (PROM), erasableprogrammable read-only memory (EPROM), electrically erasable PROM(EEPROM), registers, and so forth, including combinations thereof.

Data and instructions may be stored in the memory 1806. The instructionsmay include one or more programs, routines, sub-routines, functions,procedures, etc. The instructions may include a single computer-readablestatement or many computer-readable statements. The instructions may beexecutable by the processor 1804 to implement one or more of themethods, operations, functions and/or procedures described above.Executing the instructions may involve the use of the data that isstored in the memory 1806.

The barcode reader 1802 may include several components that maycollectively be referred to as a camera 1808. Illumination components1810 within the camera 1808 may be activated by control circuitry 1809so as to illuminate a target area. The illumination components 1810 maybe configured to provide illumination having different illuminationcharacteristics (e.g., by changing the intensity, wavelength, angle,and/or diffusion characteristics of the illumination), as describedpreviously. The illumination components 1810 may be included in aplurality of different illumination systems having differentillumination characteristics (e.g., a bright field illumination system,a diffuse bright field illumination system, and a dark fieldillumination system). Alternatively, the illumination components 1810may be included within a single illumination system that is configuredto provide illumination having different illumination characteristics.The illumination components 1810 may include light-emitting diodes(LEDs) and appropriate control circuitry. One or more lenses 1812 withinthe camera 1808 may focus light reflected from item(s) within the targetarea (e.g., a barcode) onto a photo sensor array 1814. The photo sensorarray 1814 may be a solid-state photo-detecting device containing arelatively large number of light-sensitive pixels that are arranged inhorizontal rows and vertical columns. Read-out circuitry 1816 mayelectronically read the pixels within the photo sensor array 1814 inorder to obtain a digital image.

The barcode reader 1802 may include one or more user controls 1818 thatmay be used to provide user input. Examples of different kinds of usercontrols 1818 include one or more buttons, a touchscreen, a keyboard(actual and/or virtual), a microphone, a trackball, a lightpen, etc.

The barcode reader 1802 may include a display 1820. The display 1820 mayutilize any suitable image projection technology, such as a liquidcrystal display (LCD), light-emitting diode (LED), gas plasma,electroluminescence, etc. The display 1820 may be a touchscreen. Adisplay controller may also be provided, for converting data stored inthe memory 1806 into text, graphics, and/or moving images (asappropriate) shown on the display 1820.

The barcode reader 1802 may include one or more communication interfacesfor communicating with other electronic devices. For example, thebarcode reader 1802 may include a wireless modem 1822 that allows thebarcode reader 1802 to be connected to a wireless network.Alternatively, or in addition, the barcode reader 1802 may include awired communication interface 1824 (e.g., a USB interface).

Another embodiment of the barcode readers discussed previously will nowbe described in relation to FIGS. 19-21. In this embodiment the cameraassembly 103 (FIGS. 1 and 5, 6 and 7) includes a first lens assembly1904 a and a second lens assembly 1904 b in place of the single lens 104in the camera assembly 103.

In the following discussion, unless otherwise indicated, the term “fieldof view” may refer to the field of view of the first lens assembly 1904a, the second lens assembly 1904 b, the image sensor 1902, and/or thebarcode reader 1900.

Reference is initially made to FIG. 19, which illustrates a front viewof the barcode reader with this alternative embodiment camera assembly(referred to as barcode reader 1900). The barcode reader 1900 includes adark field illumination system, a diffuse bright field illuminationsystem and a bright field illumination system. (The bright fieldillumination system may alternatively be referred to as a direct brightfield illumination system.) Each of these illumination systems directsillumination into the field of view. The illumination emitted by thedark field illumination system may be referred to herein as dark fieldillumination, and it may be similar to the dark field illuminationsystems described above in connection with FIGS. 1, 5, 6, 7, 8A, and 8B.The illumination emitted by the diffuse bright field illumination systemmay be referred to herein as diffuse bright field illumination, and itmay be similar to the diffuse bright field illumination described abovein connection with FIGS. 1, 2A, 2B, 2C, 2D, 2E, 3A, 3B, 3C, 3D, 3E, 3F,4A, 4B, 4C, 5, 6, and 7. The illumination emitted by the bright fieldillumination system may be referred to herein as bright fieldillumination (and/or direct bright field illumination), and it may besimilar to the bright field illumination 112 described above inconnection FIGS. 1, 5, 6 and 7.

The dark field illumination system includes a first set of illuminationsources 1952 a positioned behind optics 1954 a, and a second set ofillumination sources 1952 b positioned behind optics 1954 b as describedin FIG. 1, adjacent to the optics as described in FIG. 8A and/or behindthe optics as described in FIG. 8B. The diffuse bright fieldillumination system includes an optical substrate 1922 and illuminationsources 1920 a-d in the manner described with respect to FIGS. 1 and 2A.Alternatively the diffuse bright field illumination system may be any ofthe embodiments described in FIGS. 1, 2A, 2B, 2C, 2D, 2E, 3A, 3B, 3C,3D, 3E, 3F, 4A, 4B, 4C, 5, 6, and 7. The bright field illuminationsystem includes illumination sources (not shown) positioned behindrefracting diffusors 1910 a-b in the manner described with respect toFIG. 1. Alternatively the bright field illumination system may be any ofthe embodiments described in FIGS. 1, 5, 6, and 7.

The optics 1954 a-b may utilize refraction, diffusion, prismatic effect,and/or total internal reflection to direct the dark field illumination156 into the field of view. If the optics 1954 a-b utilize diffusion,and if the optics 1954 a-b are positioned in front of the illuminationsources 1952 a-b (as shown in FIG. 19), then the optics 1954 a-b may bereferred to as back lit diffusors or back lit illumination diffusors. Ifthe optics 1954 a-b utilize both refraction and diffusion, then theoptics 1954 a-b may be referred to as refracting diffusors.

The dark field illumination 156 and the bright field illumination 112may have a first illumination spectrum, and the diffuse bright fieldillumination 124 may have a second illumination spectrum that isdifferent than the first illumination spectrum. More specifically, theillumination sources 1952 a-b of the dark field illumination system andthe illumination sources of the bright field illumination system mayemit electromagnetic radiation within a first range of wavelengths, andthe illumination sources 1920 a-d of the diffuse bright fieldillumination system may emit electromagnetic radiation within a secondrange of wavelengths. Thus, the dark field illumination system and thebright field illumination system may each illuminate at least part ofthe field of view with a first illumination spectrum, and the diffusebright field illumination system may illuminate at least part of thefield of view with a second illumination spectrum. The secondillumination spectrum may be broader than the first illuminationspectrum. For example, the first illumination spectrum may includeelectromagnetic radiation primarily from 650 nm to 700 nm, and thesecond illumination spectrum may include electromagnetic radiationprimarily from 400 nm to 700 nm.

In one embodiment, an illumination spectrum includes electromagneticradiation primarily within a specified range if at least 90% of theelectromagnetic radiation within the illumination spectrum is within thespecified range. In another embodiment, an illumination spectrumincludes electromagnetic radiation primarily within a specified range ifat least 75% of the electromagnetic radiation within the illuminationspectrum is within the specified range. In another embodiment, anillumination spectrum includes electromagnetic radiation primarilywithin a specified range if a majority (i.e., more than 50%) of theelectromagnetic radiation within the illumination spectrum is within thespecified range.

Reference is now made to FIG. 20, which illustrates a side view of thebarcode reader 1900. As mentioned previously, the barcode reader 1900includes a first lens assembly 1904 a and a second lens assembly 1904 bin place of the single lens 104 in the camera assembly 103. The lensassemblies 1904 a-b may be focused to the same focal length.

In the depicted embodiment, the first and second lens assemblies 1904a-b each include a single optical lens. However, as used herein, theterm “lens assembly” refers to a set of one or more optical lenses.Thus, in an alternative embodiment, the first lens assembly 1904 aand/or the second lens assembly 1904 b could include multiple opticallenses.

The barcode reader 1900 includes an image sensor 1902, which isconfigured to capture an image of an object (e.g., a barcode) that ispositioned within the field of view. The lens assemblies 1904 a-b eachprovide a corresponding image of the object (e.g., the barcode) on theimage sensor 1902. There is a first optical path 1906 a from the fieldof view through the first lens assembly 1904 a to a first section (orportion) 1902 a of the image sensor 1902. There is a second optical path1906 b (which is different from the first optical path 1906 a) from thefield of view through the second lens assembly 1904 b to a secondsection (or portion) 1902 b of the image sensor 1902. The first andsecond optical paths 1906 a-b are substantially parallel to one another.The first lens assembly 1904 a provides a first image of the object onthe first section/portion 1902 a of the image sensor 1902, and thesecond lens assembly 1904 b provides a second image of the object on thesecond section/portion 1902 b of the image sensor 1902.

Stated another way, the first lens assembly 1904 a has a first field ofview and a first optical path 1906 a for illumination from the firstfield of view to project to a first section/portion 1902 a of the imagesensor 1902. The second lens assembly 1904 b has a second field of viewand a second optical path 1906 b for illumination from the second fieldof view to project to a second section/portion 1902 b of the imagesensor 1902.

Alternatively, as shown in FIG. 21, the barcode reader 1900 may includea first image sensor 2102 a and a second image sensor 2102 b, which maycollectively be referred to as an image sensor 2102. The first imagesensor 2102 a may be considered to be a first section (or portion) ofthe image sensor 2102, and the second image sensor 2102 b may beconsidered to be a second section (or portion) of the image sensor 2102.The first optical path 1906 a may extend from the field of view throughthe first lens assembly 1904 a to the first image sensor 2102 a. Thesecond optical path 1906 b may extend from the field of view through thesecond lens assembly 1904 b to the second image sensor 2102 b.

Referring again to FIG. 19, the center of the optical substrate 1922includes two openings 1912 a-b through which an object (e.g., a barcode)within the field of view may be visible to the lens assemblies 1904 a-band the image sensor 1902. As shown in FIG. 19, the illumination sources1952 b are positioned to the right side (when facing the barcode reader1900) of the lens assemblies 1906 a-b. The illumination sources 1952 aare positioned to the left side of the lens assemblies 1904 a-b.

The barcode reader 1900 includes control circuitry, which may be similarto the control circuitry 1809 discussed above in relation to the barcodereader 1802 shown in FIG. 18. The control circuitry 1809 mayindependently control the intensity of the illumination sources 1952a-b. More specifically, the control circuitry 1809 may be able to adjustthe intensity of the illumination sources 1952 a without affecting theintensity of the illumination sources 1952 b, and vice versa.

Referring again to FIG. 20, the first optical path 1906 a includes afilter 1910. The filter 1910 is configured to pass a spectrum ofelectromagnetic radiation that may be referred to herein as anacceptance spectrum of electromagnetic radiation. In addition, thefilter 1910 is configured to attenuate a spectrum of electromagneticradiation that may be referred to herein as an attenuated spectrum ofelectromagnetic radiation.

As indicated above, the dark field illumination 156 may have a firstillumination spectrum. The first illumination spectrum may include theacceptance spectrum. In some embodiments, the first illuminationspectrum may primarily be composed of the acceptance spectrum. In oneembodiment, the first illumination spectrum may be identical orsubstantially identical (e.g., at least 90% identical) to the acceptancespectrum. In another embodiment, there may be at least a 80% overlapbetween the first illumination spectrum and the acceptance spectrum. Inanother embodiment, there may be at least a 60% overlap between thefirst illumination spectrum and the acceptance spectrum. The attenuatedspectrum may include frequencies of visible light that are not includedin the first illumination spectrum.

The first lens assembly 1904 a and the filter 1910 may collectively bereferred to as a first set of imaging optics. The second lens assembly1904 b may be referred to as a second set of imaging optics. The firstset of imaging optics may provide a first image of an object (e.g., abarcode) on the image sensor 1902. The second set of imaging optics mayprovide a second image of the object on the image sensor 1902. Becausethe first set of imaging optics includes a filter 1910 and the secondset of imaging optics does not, the first set of imaging optics and thesecond set of imaging optics respond differently to the differentillumination spectrums of the dark field illumination system, thediffuse bright field illumination system and the bright fieldillumination system.

More specifically, the first set of imaging optics (including the firstlens assembly 1904 a and the filter 1910) may be configured so that itfocuses an image of an object (e.g., a barcode) within the field of viewwith a superior contrast profile when the object is illuminated by thedark field illumination system and/or the bright field illuminationsystem as compared to when the object is illuminated by the diffusebright field illumination system.

Conversely, the second set of imaging optics (including the second lensassembly 1904 b) may be configured so that it focuses an image of anobject (e.g., a barcode) within the field of view with a superiorcontrast profile when the object is illuminated by the diffuse brightfield illumination system as compared to when the object is illuminatedby the dark field illumination system and/or the bright fieldillumination system.

As used herein, the phrase “superior contrast profile” means at leastone of: (i) greater maximum amplitude between the portions of the imagethat are dark marks of the barcode and the portions of the image thatare light marks of the barcode; and (ii) more distinct transitionsbetween portions of the image that are dark marks of the barcode and theportions of the image that are light marks of the barcode.

Having different sets of imaging optics that respond differently to thedifferent illumination spectrums of the dark field illumination system,the diffuse bright field illumination system and the bright fieldillumination system may enable the barcode reader 1900 to be used forreading barcodes that are printed (or otherwise created) using diversetechnologies, including direct part marking.

The combination of the dark field illumination 156 and/or the brightfield illumination 112 and the first set of imaging optics may beoptimal (compared to other possible combinations of illumination andoptics) for reading certain types of barcodes. For example, if thespectrum of the dark field illumination 156 and/or the bright fieldillumination 112 is substantially from 650-700 nm, and the acceptancespectrum of the filter 910 is primarily from 650-700 nm, the combinationof the dark field illumination 156 and/or the bright field illumination112 and the first set of imaging optics may be optimal for readingbarcodes formed via copper marking on a red or green background. Morespecifically, in a captured image of a barcode formed via copper markingon a red background, this combination may cause the background to appearwhite and the barcode to appear dark. In a captured image of a barcodeformed via copper marking on a green background, this combination maycause the background to appear dark and the barcode to appear white.

Conversely, the combination of the diffuse bright field illumination 124and the second set of imaging optics may be optimal (compared to otherpossible combinations of illumination and optics) for reading othertypes of barcodes. For example, because the second set of imaging opticsdoes not include a filter 1910, the second set of imaging optics may bepreferable for reading barcodes of a certain color (e.g., red). Asanother example, the combination of the diffuse bright fieldillumination 124 and the second set of imaging optics may be optimal forreading barcodes that include dark ink on a green printed circuit board.In a captured image of such a barcode, this combination may cause thebarcode to appear dark against a light background.

The filter 1910 in the first set of imaging optics may increase contrastbetween the portions of the image that are dark marks of the barcode andthe portions of the image that are light marks of the barcode. Thefilter 1910 may also eliminate ambient noise. Therefore, the image thatthe first set of imaging optics projects onto the first section/portion1902 a of the image sensor 1902 may not have distortions caused byambient illumination. Conversely, the image that the second set ofimaging optics projects onto the second section/portion 1902 b of theimage sensor 1902 may include distortions caused by ambientillumination.

The barcode reader 1900 may include a housing that is similar to thehousing 101 of the barcode reader 100 shown in FIG. 1. The first set ofimaging optics and the second set of imaging optics may be positionedwithin the housing 101 such that the first optical path 1906 a passesthrough the first set of imaging optics (including the first lensassembly 1904 a and the filter 1910) to the first section (or portion)1902 a of the image sensor 1902, and the second optical path 1906 bpasses through the second set of imaging optics (including the secondlens assembly 1904 b) to the second section (or portion) 1902 b of theimage sensor 1902. The illumination sources 1952 b of the dark fieldillumination system are positioned to the right side of the first andsecond sets of imaging optics, and the illumination sources 1952 a ofthe dark field illumination system are positioned to the left side ofthe first and second sets of imaging optics.

The first section/portion 1902 a of the image sensor 1902 may correspondto approximately a first half of the image sensor 1902, and the secondsection/portion 1902 b of the image sensor 1902 may correspond toapproximately a second half of the image sensor 1902. In one embodiment,the phrase “approximately . . . half of the image sensor 1902” refers to45-55% of the image sensor 1902. In another embodiment, the phrase“approximately . . . half of the image sensor 1902” refers to 40-60% ofthe image sensor 1902.

The illumination sources 1952 a-b and optics 1954 a-b may be positionedsimilarly to the illumination sources 152 a-b and optics 154 a-b in thebarcode reader 100 shown in FIG. 1. Thus, the angle and direction atwhich the dark field illumination system of the barcode reader 1900emits the dark field illumination 156 may be similar to the angle anddirection at which the dark field illumination system of the barcodereader 100 emits the dark field illumination 156. Accordingly, the darkfield illumination system of the barcode reader 1900 may emit dark fieldillumination 156 towards the first optical path 1906 a at an angle(which may be referred to herein as an emission angle) that is less than45 degrees from a plane that is perpendicular to the first optical path1906 a.

Stated another way, the dark field illumination system of the barcodereader 1900 may emit dark field illumination 156 into the field of viewat an angle that is less than 45 degrees from a plane that isperpendicular to an optical path 1906 a, where the optical path 1906 aextends from the image sensor 1902 through the first set of imagingoptics (including the first lens assembly 1904 a and the filter 1910)into the center of the field of view of the first set of imaging optics.

In some embodiments, the optics 1954 a-b may comprise back litillumination diffusors that project dark field illumination 156 into thefield of view at an angle that is less than 45 degrees from a plane thatis perpendicular to the first optical path 1906 a.

The illumination sources 1920 a-d and the optical substrate 1922 may bepositioned similarly to the illumination sources 120 a-d and the opticalsubstrate 122 in the barcode reader 100 shown in FIG. 1. Thus, the angleand direction at which the diffuse bright field illumination system ofthe barcode reader 1900 emits the diffuse bright field illumination 124may be similar to the angle and direction at which the diffuse brightfield illumination system of the barcode reader 100 emits the diffusebright field illumination 124. Accordingly, the diffuse bright fieldillumination system of the barcode reader 1900 may emit diffuse brightfield illumination 124 substantially parallel to the optical paths 1906a-b.

The illumination sources and diffusors 1910 a-b of the bright fieldillumination system may be positioned similarly to the illuminationsources 108 a-b and diffusors 110 a-b in the barcode reader 100 shown inFIG. 1. Thus, the angle and direction at which the bright fieldillumination system of the barcode reader 1900 emits the bright fieldillumination 112 may be similar to the angle and direction at which thebright field illumination system of the barcode reader 100 emits thebright field illumination 112. In one embodiment, the bright fieldillumination system of the barcode reader 1900 may emit bright fieldillumination 112 substantially parallel to the optical paths 1906 a-b.In another embodiment, illumination from the illumination sources mayenter the refracting diffusors 1910 a-b at an entry angle that issubstantially parallel to the second optical path 1906 b. The brightfield illumination 112 may exit the refracting diffusors 1910 a-b towardthe field of view at a converging angle (e.g., 30 degrees or less).

As shown in FIG. 20, the dark field illumination system of the barcodereader 1900 is positioned outside of the field of view. Morespecifically, FIG. 20 shows component 1913 b, which is positioned behindillumination sources 1952 b (as shown in FIG. 19). The diffuse brightfield illumination system and the bright field illumination system arepositioned between the lens assemblies 1904 a-b and a point from whichthe dark field illumination system projects the dark field illumination156 into the field of view. The diffuse bright field illumination systemand the bright field illumination system are outside of the field ofview.

The dark field illumination system projects the dark field illumination156 into the field of view at a first angle from the first optical path1906 a. This first angle may be less than 45 degrees from a plane thatis perpendicular to the first optical path 1906 a. The diffuse brightfield illumination system projects diffuse bright field illumination 124and the bright field illumination system projects bright fieldillumination 112 into the field of view at a second angle from thesecond optical path 1906 b. The second angle may be different than thefirst angle. For example, the second angle may be substantially parallelto the second optical path 1906 b.

In an alternative embodiment, the dark field illumination system of thebarcode reader 1900 may be configured similarly to any of the other darkfield illumination systems described previously. For example, in placeof the optics 1954 a-b, the dark field illumination system of thebarcode reader 1900 may include refracting diffusors that take the formof light pipes 788 a-b having chamfered ends 778 a-b (as shown in FIG.5). Illumination sources 1952 a-b may project illumination 776 a-b intothe light pipes 788 a-b at an angle (which may be referred to herein asan entry angle) that is substantially parallel to the first optical path1906 a. The chamfered ends 778 a-b may re-direct the illumination 776a-b so that the dark field illumination 156 exits the light pipes 788a-b and is emitted toward the first optical path 1906 a at an emissionangle that is different than the entry angle. The emission angle may beless than 45 degrees from a plane that is perpendicular to the firstoptical path 1906 a.

In another embodiment, the dark field illumination system of the barcodereader 1900 may include an optical substrate 811 (as shown in FIG. 8A).Illumination sources 813 a-b may project illumination 815 a-b into theoptical substrate 811 from the side, and this illumination 815 a-b maybe internally reflected within the substrate 811 and emitted as the darkfield illumination 156. In this embodiment, the entry angle (i.e., theangle at which the illumination sources 813 a-b project illumination 815a-b into the optical substrate 811) is substantially perpendicular tothe emission angle (i.e., the angle at which the dark field illumination156 is emitted toward the first optical path 1906 a).

The optical substrate 1922 includes a front major surface 1940 and aback major surface 1938, which may be similar to the front major surface140 and the back major surface 138 of the optical substrate 122. Thefront major surface 1940 and the back major surface 1938 are bothsubstantially perpendicular to the optical paths 1906 a, 1906 b. Thefront major surface 1940 faces the field of view. The illuminationsources 1920 a-d propagate illumination between the front major surface140 and the back major surface 138.

The optical substrate 1922 may include extraction features that aresimilar to any of the extraction features 142 described above inconnection with the optical substrate 122. These extraction features 142cause the diffuse bright field illumination 156 to exit the front majorsurface 1940 into the field of view.

As used herein, the phrase “substantially parallel” means within fivedegrees of parallel. In another embodiment, substantially parallel meanswithin 15 degrees of parallel. In another embodiment, substantiallyparallel means within 20 degrees of parallel.

As used herein, the phrase “substantially perpendicular” means withinfive degrees of perpendicular. In another embodiment, substantiallyperpendicular means within 15 degrees of perpendicular. In anotherembodiment, substantially perpendicular means within 20 degrees ofperpendicular.

As used herein, the term “determining” encompasses a wide variety ofactions and, therefore, “determining” can include calculating,computing, processing, deriving, investigating, looking up (e.g.,looking up in a table, a database or another data structure),ascertaining and the like. Also, “determining” can include receiving(e.g., receiving information), accessing (e.g., accessing data in amemory) and the like. Also, “determining” can include resolving,selecting, choosing, establishing and the like.

As used herein, the phrase “based on” does not mean “based only on,”unless expressly specified otherwise. In other words, the phrase “basedon” describes both “based only on” and “based at least on.”

One or more of the features, functions, procedures, operations,components, elements, structures, etc., described in connection with anyone of the configurations described herein may be combined with one ormore of the functions, procedures, operations, components, elements,structures, etc., described in connection with any of the otherconfigurations described herein, where compatible.

The steps and/or actions of the methods described herein may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isrequired for proper operation of the method that is being described, theorder and/or use of specific steps and/or actions may be modifiedwithout departing from the scope of the claims.

The claims are not limited to the specific implementations describedabove. Various modifications, changes and variations may be made in thearrangement, operation and details of the implementations describedherein without departing from the scope of the claims.

What is claimed is:
 1. A barcode reader, comprising: a firstillumination system that emits first illumination with a firstillumination spectrum; a second illumination system that emits secondillumination with a second illumination spectrum, the secondillumination spectrum being broader than the first illuminationspectrum; a first lens assembly with a first optical path through thefirst lens assembly to a first image sensor section, the first opticalpath including a first filter configured to pass a first filter spectrumof electromagnetic radiation and attenuate a second filter spectrum ofelectromagnetic radiation, wherein the first illumination spectrum isprimarily composed of the first filter spectrum; and a second lensassembly with second optical path through the second lens assembly to asecond image sensor section.
 2. The barcode reader of claim 1, whereinthe second filter spectrum includes frequencies of visible light notincluded in the first illumination spectrum.
 3. The barcode reader ofclaim 1, wherein the first illumination spectrum includeselectromagnetic radiation primarily from 650 nm to 700 nm.
 4. Thebarcode reader of claim 1, wherein the second illumination spectrumincludes electromagnetic radiation primarily from 400 nm to 700 nm. 5.The barcode reader of claim 1, wherein the first illumination system isa dark field illumination system, the dark field illumination systememitting the first illumination towards the first optical path at anemission angle that is less than 45 degrees from a plane that isperpendicular to the first optical path.
 6. The barcode reader of claim5, wherein the dark field illumination system comprises a first set ofillumination sources positioned to a right side of the first and secondlens assemblies and a second set of illumination sources positioned to aleft side of the first and second lens assemblies.
 7. The barcode readerof claim 6, further comprising control circuitry that independentlycontrols intensity of the first set of illumination sources and thesecond set of illumination sources.
 8. The barcode reader of claim 6,wherein the dark field illumination system comprises a back litillumination diffusor emitting the first illumination towards the firstoptical path at the emission angle.
 9. The barcode reader of claim 6,wherein: the dark field illumination system comprises a refractingdiffusor through which the first illumination is emitted towards thefirst optical path at the emission angle; and illumination enters therefracting diffusor at an entry angle that is different than theemission angle.
 10. The barcode reader of claim 9, wherein the entryangle is substantially parallel to the first optical path.
 11. Thebarcode reader of claim 9, wherein the entry angle is substantiallyperpendicular to the emission angle.
 12. The barcode reader of claim 1,wherein the second illumination system is a diffuse bright fieldillumination system comprising: an optical substrate with a front majorsurface and a back major surface, each of which is substantiallyperpendicular to an optical path of the barcode reader, the front majorsurface facing a field of view of the first and second lens assemblies;at least one illumination source propagating illumination between thefront major surface and the back major surface; and extraction featurescausing the second illumination to exit the front major surface into thefield of view of the first and second lens assemblies.
 13. A barcodereader, comprising: an image sensor configured to capture an image of abarcode within a field of view of the image sensor; a first set ofimaging optics and a second set of imaging optics, each for providing acorresponding image of the barcode on the image sensor; and a firstillumination system and a second illumination system, each forilluminating at least a part of the field of view with a respectivefirst illumination spectrum and a second illumination spectrum differentfrom the first illumination spectrum, wherein the first set of imagingoptics and the second set of imaging optics respond differently to thedifferent illumination spectrums.
 14. The barcode reader of claim 13,further comprising a housing, wherein the first set of imaging opticsand the second set of imaging optics are positioned within the housingsuch that there is a first optical path through the first set of imagingoptics to a first portion of the image sensor and a second optical paththrough the second set of imaging optics to a second portion of theimage sensor.
 15. The barcode reader of claim 14, wherein the firstoptical path is different from the second optical path.
 16. The barcodereader of claim 14, wherein the first portion of the image sensorcorresponds to approximately a first half of the image sensor and thesecond portion of the image sensor corresponds to approximately a secondhalf of the image sensor.
 17. The barcode reader of claim 14, whereinthe image sensor comprises a first image sensor and a second imagesensor, the first image sensor including the first portion of the imagesensor and the second image sensor including the second portion of theimage sensor.
 18. The barcode reader of claim 13, wherein the first setof imaging optics includes a filter configured to pass a first filterspectrum of electromagnetic radiation and attenuate a second filterspectrum of electromagnetic radiation.
 19. The barcode reader of claim18, wherein the first illumination spectrum includes the first filterspectrum.
 20. The barcode reader of claim 18, wherein the firstillumination spectrum is primarily composed of the first filterspectrum.
 21. The barcode reader of claim 18, wherein the second filterspectrum includes frequencies of visible light not included in the firstillumination spectrum.
 22. The barcode reader of claim 18, wherein thefirst illumination spectrum includes electromagnetic radiation primarilyfrom 650 nm to 700 nm.
 23. The barcode reader of claim 18, wherein thesecond illumination spectrum includes electromagnetic radiationprimarily from 400 nm to 700 nm.
 24. The barcode reader of claim 13,wherein: the first illumination system includes a bright fieldillumination system that directs bright field illumination having thefirst illumination spectrum into the field of view of the image sensor;the first illumination system also includes a dark field illuminationsystem that directs dark field illumination into the field of view ofthe image sensor; and the second illumination system includes a diffusebright field illumination system that directs diffuse bright fieldillumination having the second illumination spectrum into the field ofview of the image sensor.
 25. The barcode reader of claim 24, whereinthe bright field illumination system and the diffuse bright fieldillumination system direct illumination into the field of view of theimage sensor substantially parallel to an optical path that runs througha set of imaging optics to a portion of the image sensor.
 26. A barcodereader, comprising: a first illumination system that emits illuminationwith a first illumination spectrum; a second illumination system thatemits illumination with a second illumination spectrum; an image sensorconfigured to capture an image of a barcode within a field of view ofthe image sensor; and a first set of imaging optics and a second set ofimaging optics, each providing a corresponding image of the barcode onthe image sensor; wherein the first set of imaging optics is configuredto focus an image of the barcode, when illuminated by the firstillumination system, with a superior contrast profile than whenilluminated by the second illumination system; wherein the second set ofimaging optics is configured to focus an image of the barcode, whenilluminated by the second illumination system, with a superior contrastprofile than when illuminated by the first illumination system; andwherein superior contrast profile means at least one of: (i) greatermaximum amplitude between the portions of the image that are dark marksof the barcode and the portions of the image that are light marks of thebarcode; and (ii) more distinct transitions between portions of theimage that are dark marks of the barcode and the portions of the imagethat are light marks of the barcode.
 27. The barcode reader of claim 26,wherein the first illumination system is a dark field illuminationsystem, the dark field illumination system emitting the illumination ofthe first illumination spectrum into the field of view of the imagesensor at an angle that is less than 45 degrees from a plane that isperpendicular to an optical path from the image sensor through the firstset of imaging optics into a center of a field of view of the first setof imaging optics.
 28. The barcode reader of claim 27, wherein the darkfield illumination system comprises a first set of illumination sourcespositioned to a right side of the first and second sets of imagingoptics and a second set of illumination sources positioned to a leftside of the first and second sets of imaging optics.
 29. The barcodereader of claim 28, further comprising control circuitry thatindependently controls intensity of the first set of illuminationsources and the second set of illumination sources.
 30. The barcodereader of claim 28, wherein the dark field illumination system comprisesa back lit illumination diffusor emitting the first illumination towardsthe first optical path at the emission angle.
 31. The barcode reader ofclaim 28, wherein: the dark field illumination system comprises arefracting diffusor through which the first illumination is emittedtowards the first optical path at the emission angle; and illuminationenters the refracting diffusor at an entry angle that is different thanthe emission angle.
 32. The barcode reader of claim 31, wherein theentry angle is substantially parallel to the first optical path.
 33. Thebarcode reader of claim 31, wherein the entry angle is substantiallyperpendicular to the emission angle.
 34. The barcode reader of claim 26,wherein the second illumination system is a diffuse bright fieldillumination system comprising: an optical substrate with a front majorsurface and a back major surface, each of which is substantiallyperpendicular to an optical path of the barcode reader, the front majorsurface facing a field of view of the first and second lens assemblies;at least one illumination source propagating illumination between thefront major surface and the back major surface; and extraction featurescausing the second illumination to exit the front major surface into thefield of view of the first and second lens assemblies.